Alloy



Znv

Feb. 10, 1,942. E.I A. ANDERSON Em. 2,2?2-,390y

ALLOY Filed Jan. 16, 1940 3 Sheets-Sheet 1 f@ mma-awww 6B 30 vv vWW 70/0/aer ATTORNEY Feb'- 10, 1942. E. A. ANDERSON Erm. 2,272,390

Filed Jan. 1e, 1940 s 'sheets-sheet 5 INVENTOR {drm/mz A. Ande/sar? Gaming WMI/m17.;

ATTORNEYS Patented Feb. i110, 1942 UNITED STATES PAT-ENT Fries ALLGY New Jersey Application January 16, 1940, No. 314,086

e claims.

This invention relates to zinc base alloys and provides new alloys containing zinc, manganese,

. and aluminum (and, preferably, also copper) having superior mechanical properties. The a1- loys of our in vention have an appearance similar to that of white metal alloys.

As a result of our investigations, we have discovered new zinc alloys containing certain proportions of manganese, and aluminum (and prei'- erably also copper) which, as cast, have an impact strength of about one foot-pound per onequarter square inch cross section or more, a tensile strength of about 60,000 pounds per square inch or higher. and high creep resistance. They may be formed into intricate shapes of accurate configuration by die casting, and are also amenable to casting by other methods.

vAll percentages given hereinafter are percentages by weight, and on this basis the alloys of our invention contain aluminum in proportions ranging from 0.02% to about 5% (but preferably from 0.1 to 2%), together with manganese in the proportions ranging from about 7.5% to about 48.5%, and (preferably) copper in proporcontents, but in general the alloys should not 30 contain more than about 6% of iron.

In the manufacture of the alloys of our invention, it is not essential in all cases to employ high grade manganese, for the impurities` that may occur in the ordinary commercial grades 35 of manganese may be included in our alloys in some cases without too serious eect uponJ the properties thereof. Manganese suitable for use in the practice of our invention may contain minor proportions of silicon, phosphorus, carbon, .40

nitrogen, and other impurities. We prefer, however, to use manganese of high purity, since impurities in the manganese may degradethe mechanical properties of" the alloy and, in particu- The alloys of our invention, their composition, and theirmechanical properties, particularly in cold chamber die-cast form, are described more fully hereinafter with reference to the accompanyig drawings, Figs. 1, 2, and 3, which are trillnear charts representing the zinc corner of the Zn- Cu-Mn system, extending to 30% Cu and 50% Mn and in which:

Fig, 1 shows the approximate proportions of zinc, copper and manganese to be employed (together with certain proportions of aluminum) in the manufacture of alloys of our invention having impact strengths of about 1 foot-pound or more per one-quarter inch square cross section, (inthe specification and claims the term impact strength refers to values obtained in a Charpy impact test on unnotched test bars) and tensile strengths of about 60,000 pounds per square inch or better;

Fig'. Z'shows the impact strength of the alloys by means of contour lines; and

Fig. 3 shows the Brinell hardness numbers of certain alloys of our invention.

In Fig. 1, the contour line A' demarcates the range of composition in which the alloys have a tensile strength of 60,000 pounds per square inch or better.` The contour line B demarcates the range of composition in which the alloys have a tensile strength of 70,000 pounds per squareinch or better. The contour line C encloses the range of composition in which th alloys have a tensile strength of 80,000 pounds per square inch or better. The contour line D' encloses the area in which the alloys have a tensile strength of Y poor side of which difficulties are encountered in lar, cause the presence of hard particlesthat 5 ,the Prepration and Casting of the alloys. It

may interfere with machining and bullas.

- willbe noted that the contour lines A' and B' do not enclose an area, being open towards the manganese corner of the diagram. The line E", however, closes the areas delimited by contour lines A', and B. Thus, the area delimited by A' and E'" contains useful alloy compositions having a tensile strength of 60,000 pounds per square inch or better, and the area delimited by B' and E'" contains useful alloy compositions having a tensile strength of '10,000 pounds per square inch or better.

In Fig. 2, the contour line E indicates the range of composition of alloys having an impact strength of 1 foot-pound or more per one-quarter inch square cross section. As has been explained in the discussion of Fig. 1, the straight dotted lines E" and E" show limits beyond which towards the zinc-poor field of 'alloy compositions dificulties are encountered in the preparation and casting of the alloys. Contour line F' indicates the range of composition of alloys having an impact strength of 2 foot-pounds or more per one-quarter inch square cross section. Contour line G indicates the range of composition of alloys having an impact strength of 4 foot-pounds or more per one-quarter inch square cross secy tion. The areas enclosed by contour linesF' and G' are closed by the straight boundary E" Contour line H encloses the range of composition in which the alloys have an impact strength of 8 foot-pounds or more per one-quarter inch contour A' (drawn through points representing4 the composition of alloys having tensile strength of about 60,000 pounds) and the contour line E (drawn through points representing the composition of alloys having impact strength of about 1 foot-pound per one-quarter inch square bar) are roughly coincident and dene approximately the same area. In short, the alloys ofour invention have tensile strengths of about 60,000 pounds persquare inch or more, together withl impact strengths of about 1 foot-pound plus. The values in Tables I and II represent points on both contours A and E', depending upon which is outermost on the chart. Thus, in order to obtain alloys that may be cast readily and that have, as cast, tensile strength of approximately 60,000 pounds per square inch or more and impact strength of about 1 foot-pound per one-quarter inch square section or more, the approximate manganese ranges for given copper contents are as follows:

' invention containing 0.15%

To express the relationship of copper and manganese contents in another way, the approximate limits of copper content for. given manganese contents are as follows: l

As shown in Fig. ,1 (area A) an alloy of our aluminum, 38%- 48.5% manganese, and substantially no copper, the balance being substantially all zinc, has a tensile strength as cast of about 60,000 pounds per square inch (points 10'-10"). The same tensile strength is found in alloys with the same aluminum content but with various proportions of manganese and copper as follows:

Area A, Boundary "Am Approximate analyses of alloys having tensile strength ol about 00,000 pounds per Point on Fir. 1 sqm meh Per cent Por cent Per cent Al Cu Mn Still higher tensile strengths are obtainable by differently proportioning the manganese and copper contents of the alloys of our invention.

Certain of the alloys of our invention have, as cast, tensile strengths of about 70,000 pounds per square inch or higher. These alloys contain in addition to about 0.02% to about 2% aluminum, from about 1.5% to about 24% copper, and about 11% to about 48.5% manganese, the balance of th'alloy (except for a relatively small iron content) consisting essentially of zinc. In these alloys the copper and manganese contents are so related as to 'define points lying substantially in the area B on the trilinear chart (Fig. 1).

- Some of the alloysv have, as cast, a tensile 7-1-36 17-26 and also 3l the alloy as in the previous cases consisting essentially of zinc, with or without a relatively small proportion of iron, and the copper and manganese contents of the alloys being such f as to deiine a point lyin'g substantially in the area C on the trilinear chart (Fig. 1).

To obtain alloys having a tensile strength of portions ranging from about 15% to about 22%.

These lalloys have manganese and copper contents so related as to dene points lying substantially in the area D of the trilinear chart (Fig. 1)

In short, those alloys having f a tensile strength of170,000 pounds per `square inch or more, are of analyses that fall within the area B Von Fig. 1; those having a tensile strength of atleast 80,000 pounds per square inch are those having copper and manganese contents that fall Within the area 'C on Fig. 1, while those of tensile strengths of 90,000 pounds ormore per square inch are those having manganese and copper contents enclosed within the area D on Fig. 1. For example, thosel alloys containing 0.15% aluminum, 20% copper and 16% to 22.5% manganese, the balance being substantially all zinc, have tensile strengths of atleast 90,000 pounds per square inch.

It will be observed that the .range of useful alloys having impact strengths of I foot-pound or more per one-quarter inch square section is 35 deiined by the area E, enclosed by the impact strength contour line E' on the trilinear charts runningV from point I (0% Cu, 33.3% Mn) through point 24 (16% Cu, 10% Mn), point I4' (20% Cu, 7.5% Mn), point 25 (20.2% Cu, 10%:

Mn), point 26 (23% Cu, 20% Mn), point 21 (22% cu, 25.5% Mn) to point l" (25% cu, 31% Mn);

the straight line E" running from point l5 to The straight lines E and E" are not contour 50 lines, but, in the case of'compositions lying substantially above or outside these lines, i. e., on

the zinc-poor side of these lines, diiiculties are encountered in the preparation and handling of the alloys.

All of the alloys of our invention have, as shown in Fig. 2, adequately high impact strength, that is to s'ay, they are not brittle. The area F enclosed by the contour line F' on Fig. 2 indicates the proportions of copper and manganese ernployed in alloys of our invention, together with aluminum (the balance of the alloy being substantially all zinc) to obtain impact strengths of at least 2 foot-pounds in a cold ,chamber die-cast bar with acne-quarter inch square section. Still higher impact strengths (i. e., 4 foot-pounds per quarter inch-` square section, or better) are obtained` with compositions falling Within the area G .bounded by the contour line G on Fig. 2, and impact strengths of 8 foot-pounds per one-quarter inch square, or better, areA obtained with bounded by* the contour line H onFig. 2.

terms of the copper and manganese contents they represent are as follows:

5 Tensile strength,polmls persq.ln. Arca Crgggr Mgggese Per Pesr cent 0 f 56-48 B 156-24- 11 -48 C -9 22% 13K-34% D -22 1,5 -zgia Impact strength foot-pounds per Area Copper Manganese K in. square range range l-l- E 0 -25 @HBM 1 2+ F o -23 12 48% 4+ G 0 21% 16M-48% 8+ H 71/5-20 20 -38 vAs indicated by Fig. 3, the alloys of our invenwith a relatively low copper content are in general relatively soft.'

Alloys of our invention are not subject to the temperature embrittlement encountered in many zinc alloys at very low temperatures.

Thus, an alloy of our invention containing 24% to 25% manganese, '15.2%' to 15.5% copper, 0.15% to 0.18% aluminum (the remainder being special high-grade zinc of high purity) was tested for impact strength and tensile strength at low temperatures and was found netto become brittle, even at temperatures as low as 40 C.

Alloys of our invention have high creep resist- 1 ance. Alloys containing 2425% manganese,

4 15.2-15.5% copper, and L15-0.18% ammmum,

the remainder b'eing special high-grade zinc; were tested for creep resistance at 25 C. under bending stresses equivalent to maximum fiber stressesin tension up, to 70,000 poluids per 15 square inch. No creep was detected during three'days. In contrast, heretofore customary zinc base die-casting alloys suiered detectable `,creep in three days under a stress of 2,500 pounds per square inch, other conditions being the same. e

The modulus of elasticity of'alloys of our invention as indicated .by beam deilections observed during the above reported creep tests was found to be about 14,000,000 pounds per square 5 inch, `which 'greater than that of any z incl base die-casting alloys known to us. Moreover, the alloys of our invention possess 'apparent rigidity or stiiness to a degree greater than that of any other zinc alloys of reasonable 6 ductiiity.

'--` The alloys of our invention manifest goodv rev sistance to atmospheric corrosion. Further, water immersion tests of alloys containing 25% Mn, 15% Cu and 0.15% A1 (the balance being substantially all zinc) showed a corrosionresistance roughly comparable to vthat oi? the zinc -base die-casting alloys Nos. Xin, m1, and

XXV` of` A. S. T. M. tentative specications i386-'3811 1938.

The preferred group of alloys ofr our invention consists of those within the range of com- Approximate .limits of the several areas mja-positions delineated by the 8 foot-pound contour (H') on the impact strength chart (Fig. 2,

t area H). These alloys all have (as cast) tensile strengths ranging from about 75,000 to 97,000 pounds per square inch and tensile elongation values from about 1% to 6% in a two inch gage length. By way of example, the following alloys within the preferred range are cited.

Alloy I II III IV V Analysed percent Mn... 22. 2 24. 7 29. 6 34. 2 2l. 6

Analyzed percent Cu--. 17. 5 15.4 14.4 10. 0 18. 3

Analyzed percent AL... 0. l5 0.17 v0. 18 0.18 0. 14

Aualyzed percent Fe.. 0. 17 0.19 0. Zi 0.28 0. 18 Tensile strength, lbs.

per sq. in, 90,200 89,100 84,900 Si, 200 `97, 300 Tensile elongation, percent in 2 in 2 6 2 2 3 Impact strength, tootund on a M in. sq.

ar 12.9 18 12.1 11.9 12.7 Brinell hardness number 167 158 161 159 184 It will be observed that the alloys lying within the preferred range possess, as cast, remarkably superior characteristics which favor their use in the manufacture of a great variety of articles by inexpensive processes, such as die casting.

As indicated hereinbefore, aluminum is an essential ingredient in the alloys of our invention. The presence of the aluminum not only improves the casting characteristics lof the alloys, but also tends to suppress oxidation of the surfaces of the hot casting. The presence of the aluminum in the alloys of our invention enables castings made thereof to be cooled in air without serious discoloration. An unsightly brown film forms on the surface of air-cooled castings of similar Zn-Cu-Mn alloys without the aluminum. Moreover, the presence of the aluminum in the alloy within the range specified, i. e., 0.02% to about 5%, reduces dross formation on the molten alloy during casting operations and tends to impart an attractive silvery appearance to the resulting casting. When aluminum is not present, a tanaclous brown film tends to form on the molten alloy, interfering with pouring and making difficult the production of a casting having a smooth surface. However, an aluminum content of more than about 5% cannot be tolerated because of the deleterious enect thereof upon the mechanical properties of the alloys.I In case the aluminum content exceeds 2%, the' tolerance for impurities is limited. The effect of aluminum upon relative- 1y impure alloys is illustrated in the following table:

fcct of the inclusion of iron upon relatively impure alloys is shown by the following data:

Alloy X XI XII XIII A ywt r 24.4 23.5 21.0 24.0 A ,m percent Cu 16.5 14.4 13.5 16.4 A ,ym nt 0.18 0.090 0.085 Analyser percent Fe 0.19 2.2 4.9 5.4 Tensile strength, lbs. per square 88,500 83,000 87,900 71,500 Tensile elongation, percent in 2 in. 4 'e 1 o Impact strength, foot-pounds on in. .bar 18 11 4.7 3.8 B ell hardness number 150 158 158 178 molten alloy with a nonreactive gas, e. g., hydrogen.

As indicated hereinbefore, allv of the alloys of our invention can be die cast and 011er certain advantages over heretofore customary zinc a1- loys that can be die cast because of their greater strength and hardness. However, certain alloys of l'our invention have been' gravity cast in permarient metal moulds and also gravity cast in sand moulds. Although some differences in properties of the alloys of our invention are induced by the method of casting, the alloys of our invention in `general exhibit superior properties as compared with heretofore customary zinc alloys, irrespective of the particular method of casting.

1. An alloy having as cast ,an impact strength of at least about 1 foot-'pound per V4 inch square section and containing about 0.02 per cent to about 5 per cent aluminum, copper in effective amount up to about 26 per cent and about 7.5 per cent to about 48.5 per cent manganesathe balance of the'allcy being substantially all zinc and the copper and the manganese contents of the alloy being so related to each other as to` denne a point on the accompanying trilinear chart (Fig. 2) lying within the area E defined by the line connecting the following series of The inclusion of up to 6% iron inl the alloys of' our invention ispermissible. The tolerance for iron of the particular alloy depends upon its Alloy points:

VI VII VIII IX 60 Point No Per cent Cu Per cent Mn Analyzed percent of Mn 24. 7 24. 7 23.8 0 33.-,3 Analyzed percent of Cu 15.4 15. 4 15. 4 l0 10 Analyzed percent oi Al 0.021 0.45 1.2 m 7.5 Anal sed percent of Fe 0.19 0.21 0.19 20. 2 l0 'lens le strength, lbs. per square Zi 20 inch.... 90,600 86,100 89,200 22 25.5 `Tensile elongation, percent 1n 2 25 31 in 5 2 1 11 44. 5 Impact strength, loot-pounds on 0 48. 5 in. sq. bar 16 1l, 3.1 0 33.3 Brincll hardness number 166 172A 191 y 2. An alloy having as cast an impact strength 'of at least about 2 foot/pounds per V4 inch square section and containing about 0.02 per cent to about` 2 per cent aluminum, copper in effective 'amount up to about 23 per cent, and manganese in proportions ranging from about 12 per cent to Per cent Cu Per cont Mn 3. An alloy having as cast an impact strength of at least about 4 foot-pounds per Mi inch square section and containing about 0.02 per cent to about 2 per cent aluminum, copper in effective amount up to about 211/2 'per cent, and about 161/2 per cent to Iabout 481/2 per cent manganese, substantially all of the balance of the alloy being zinc, the copper and manganese contents of the alloy being such as to denne a point on the laccompanying trilinear chart (Fig. 2) lying within the area G defined by the line connecting the following series of points:

' 4. An alloy havingas cast animpact strength of at least about 8 foot-pounds per 1A inchsquare section and. containing about 0.02 per cent to about 2,per cent aluminum, about 71/2 per cent to about per cent copper, and about 20 per cent to about 38 per cent manganese, substantially all of, the balance of the alloy being zinc,

and the copper. and manganese contents of thealloy being so related as to define a point onl the accompanying-trilinear chart (Fig. 2) lying within the area H deiined bythe line .connecting the following series of points: 1

Percent Cu Percent Mn senescence. Ul

. 5. An`alloy having as' cast a tensile strength" of -at least about 60.000. pounds per square inch and containing about 0.02 per cent to about 5 per cent aluminum, copper in effective amount up to about 261/2 per cent and about 81/2 per cent to about 481/2 per cent manganese, substantially all of the balance of the alloy being zinc and the copper andl manganese contents of the alloy being such as to denne a point on the .accompanying trilinear chart (Fig. 1) lying within the area A defined by the line connecting the followin series of points:

`Point No. Percent Cu Percent Mn 6. An alloy having as cast a tensile strength of at least about 70,000 pounds per square inch and containing about 0.02 per cent to about 2 per cent aluminum, about 1.5 per cent to about 24.5 per 'centgcopper and about 1l. per cent to about 48 per cent manganese, substantially all of the balance of the alloy being zinc, the copper and manganese lcontents vof the alloy being so related as to define a point on the accompany- ,ingy trilinear chart (Fig. 1) lying within the area B 'deined by the line connecting the following series of points: l

Percent Cu Percent Mn 7. An alloy having as cast a tensile strength oi at least about 80,000 pounds per square inch and containing about 0.02 per. cent to about 2 per cent aluminum, about 9 per cent to about.

22V;4 per cent copper and about 131/2 per cent to about 341/2 per cent manganese, substantially all of the balance of the alloy being zinc and the copper and manganese contents of the alloy being such as tol define a point on the accompanylngr trilinear chart (Fig. 1)A lying within the area C dened by the line connecting the following series of points:

'.Per cent Cu Per cent Mn 8. An lalloy having as cast a tensile strength of at least about 90,000. poundaper square inch and containing about 0.02 per cent to about 2 per-cent aluminum. about 15 per cent to about 6 :masso 22 per cent copper and about 15 per cent to about 221/2 per centr manganese. substantially all o! the balance of the alloy being zinc, and the copper and manganese contents of the alloy being such as to denne a point lying within the area. D on the accompanying' trilinear chart (Fig. 1) delineated by the line D' passing through the following series of points:

Per cent Cu Per cent Mn 9. An alloy containing about 0.02 per cent to about 5 per cent aluminum and about 7.5 per cent to about`48.5 per cent manganese, substantially all ofl the balance of the alloy being elements selected from the group consisting 'of zinc and copper, the copper being present in e'ective amount upto about 26.5 per cent, and the copper and manganese contents of the alloy being such as to denne a point on the accompanying trlllncar chart (Fig. 1) lying within an arear dened by a. line connecting the following series of points:

Percent Cu Percent Mn EDMUND A. ANDERSON. GERALD EDMUNDS. 

